Add SkSourceGammaTreatment enum so we know how to create mips

src/image/SkImageShader.cpp

Index: src/image/SkImageShader.cpp
diff --git a/src/image/SkImageShader.cpp b/src/image/SkImageShader.cpp
index d12ee030a2a19a921a75d778e5521626a0f8a589..7956f3e4a8d33dc21c8b7427987f4de6a1ab140d 100644
--- a/src/image/SkImageShader.cpp
+++ b/src/image/SkImageShader.cpp
@@ -86,7 +86,8 @@ void SkImageShader::toString(SkString* str) const {
 const GrFragmentProcessor* SkImageShader::asFragmentProcessor(GrContext* context,
                                                               const SkMatrix& viewM,
                                                               const SkMatrix* localMatrix,
-                                                              SkFilterQuality filterQuality) const {
+                                                              SkFilterQuality filterQuality,
+                                                              bool gammaCorrect) const {
     SkMatrix matrix;
     matrix.setIDiv(fImage->width(), fImage->height());
 
@@ -113,7 +114,7 @@ const GrFragmentProcessor* SkImageShader::asFragmentProcessor(GrContext* context
     GrTextureParams::FilterMode textureFilterMode =
     GrSkFilterQualityToGrFilterMode(filterQuality, viewM, this->getLocalMatrix(), &doBicubic);
     GrTextureParams params(tm, textureFilterMode);
-    SkAutoTUnref<GrTexture> texture(as_IB(fImage)->asTextureRef(context, params));
+    SkAutoTUnref<GrTexture> texture(as_IB(fImage)->asTextureRef(context, params, gammaCorrect));
     if (!texture) {
         return nullptr;
     }